The present invention generally relates to semiconductor devices and more particularly to a semiconductor device having a ceramic package.
With the demand for reducing the cost of semiconductor devices, use of cheap die-bonding processes that use the conductive epoxy resin, instead of conventional aluminum-silicon braze, for bonding a semiconductor chip on a package, is spreading.
When such an epoxy resin is used for porous ceramic packages, there occurs a phenomenon called bleeding, wherein the epoxy resin penetrates into the ceramic package by the capillary phenomenon.
FIG. 1 shows a conventional ceramic package in which a semiconductor chip 5 is mounted on a depressed mounting stage part 2 of a ceramic package by a layer of a conductive epoxy resin 6. In FIG. 1, the semiconductor chip 5 has a bonding pad 4 on its upper surface, and the bonding pad 4 is connected to an interconnection lead 10 fixed on the package 1 via a bonding wire 9.
In such a structure, it is generally inevitable that a penetration or bleeding of the epoxy resin forming the layer 6 occurs such that the epoxy resin penetrates more or less into the porous ceramic package 1 as shown by a region 8. Usually, such a penetration of the resin is limited to the region within the depressed stage part 2 and does not cause any serious problem. However, it is observed that such a bleeding 8 extends occasionally beyond the stage part 2 into the region of the package 1 that surrounds the stage part 2 as shown by a region 8a. It should be noted that the region of the package 1 that surrounds the stage part 2 is provided with the interconnection lead 10, and the resin that have caused the bleeding 8a covers the interconnection lead 10. When such a coverage of the interconnection lead 10 by the resin 8a occurs, the electric interconnection by the bonding wire 9 inevitably fails. As the epoxy resin employed for such a purpose is generally made conductive by admixing conductors such as silver, such a coverage of the interconnection lead 10 by the bleeding 8a causes a short circuit connection, even when the bonding of the wire 9 is made successful. It is believed that such an unpredictable occurrence of the bleeding 8 is caused by the microstructure of the ceramic forming the package such as alumina. The control of microstructure of alumina ceramic is not yet perfect in the presently available ceramic technology.